CA1164560A - Reversible thermo-optical memory structure - Google Patents
Reversible thermo-optical memory structureInfo
- Publication number
- CA1164560A CA1164560A CA000369792A CA369792A CA1164560A CA 1164560 A CA1164560 A CA 1164560A CA 000369792 A CA000369792 A CA 000369792A CA 369792 A CA369792 A CA 369792A CA 1164560 A CA1164560 A CA 1164560A
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- Prior art keywords
- layer
- memory structure
- martensitic
- phase
- inscription
- Prior art date
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- Expired
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Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
- G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
- G11B7/244—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only
- G11B7/245—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only containing a polymeric component
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
- G11B7/0045—Recording
- G11B7/00452—Recording involving bubble or bump forming
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
- G11B7/0055—Erasing
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/2403—Layers; Shape, structure or physical properties thereof
- G11B7/24035—Recording layers
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/2403—Layers; Shape, structure or physical properties thereof
- G11B7/24067—Combinations of two or more layers with specific interrelation
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
- G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
- G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
- G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
- G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
- G11B2007/24302—Metals or metalloids
- G11B2007/24304—Metals or metalloids group 2 or 12 elements (e.g. Be, Ca, Mg, Zn, Cd)
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
- G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
- G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
- G11B2007/24302—Metals or metalloids
- G11B2007/24306—Metals or metalloids transition metal elements of groups 3-10
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
- G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
- G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
- G11B2007/24302—Metals or metalloids
- G11B2007/24308—Metals or metalloids transition metal elements of group 11 (Cu, Ag, Au)
Landscapes
- Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Optical Record Carriers And Manufacture Thereof (AREA)
- Thermal Transfer Or Thermal Recording In General (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
REVERSIBLE MEMORY STRUCTURE WITH THERMO-OPTICAL
WRITING AND OPTICAL READING AND PROCESS FOR WRITING
AND ERASING SAID STRUCTURE.
The invention relates to a reversible memory structure with thermo-optical inscription or writing and optical reading on a moving support.
According to the invention, the memory structure deposited on a substrate (1) is constituted by a double layer (2 and 3). A second allay layer (3) at ambient temperature in the martensitic phase is deposited on a first thermally deformable layer (2). A heat pulse creates a deformation in the first layer, which deforms the martensitic alloy layer. A more powerful heat pulse raises the alloy layer to a temperature above its transformation point from the martensitic phase to another crystallo-graphic phase and erases the inscribed deformation.
Particular application to optical disks.
Figure 4c
REVERSIBLE MEMORY STRUCTURE WITH THERMO-OPTICAL
WRITING AND OPTICAL READING AND PROCESS FOR WRITING
AND ERASING SAID STRUCTURE.
The invention relates to a reversible memory structure with thermo-optical inscription or writing and optical reading on a moving support.
According to the invention, the memory structure deposited on a substrate (1) is constituted by a double layer (2 and 3). A second allay layer (3) at ambient temperature in the martensitic phase is deposited on a first thermally deformable layer (2). A heat pulse creates a deformation in the first layer, which deforms the martensitic alloy layer. A more powerful heat pulse raises the alloy layer to a temperature above its transformation point from the martensitic phase to another crystallo-graphic phase and erases the inscribed deformation.
Particular application to optical disks.
Figure 4c
Description
56~;~
Reversible memor structure with thermo-o~~ic riti~
and o~cal readin~ and~~rocess for writln~ and eras-in~
~aid structure.
BACKGR0UND OF ~HE INVENTION
The present invention relates to a reversible memory structure, i.e. it can be thermo-optically written and erased, whilst reading is optica:l.
It applies more particu]arly to the inscription or writing layer of a memory storing data on a moving support. One widely used form of this memory is the optical disk. Optical disks are made from a disk of a rigid and generally kransparent material covered with a thin film of a light-absorbing material. The disk rotates at a relatively high speed and passes in front of a reading head, which detects the data which have been recorded in the surface absorbent layer. r~he data are generally stored in the form of perforations in the absorbent layer. Thus, reading can take place by passing a laser beam through the data storage holes and through the transparent support oE the op~ical disk. It can also be carried out by reAflecting a laser beam through -the transparen-t _ support of the disk onto the absorbent layer. The data can also be stored in the form of a surface defo-rmation in which case reading takes place by reflection.
The existing technology of optical disks or in more general terms moving memories has two types of structure for the t~riting or inscript:ion layer, namely non-e~asable structures such as those in which are made ~.
~ 3 perforations of the metal layer constituting the absorbent layer, or erasable structure.s Erclsable structures are based on the use of arnorphous, metallic or semiconducting materials or magneto-optic, photochromic or photodichroic materialshaving differences in the optical properties depending on whether or not they are inscribed by a laser beam. The general disadvantage o such erasable structures is a low signal~to-no;se ratio because there is no fundamental modification of the structure of the absorbent layer material.
B~IEF SUMMAR~ OF TEIE INVENTION
rfhe invention relates -to a novel reversible memory s~ructure, i.e. it can be erased and re~
inscribed, which has a better signal-to-noise ratio than the known memories. This structure is constituted by a two-layer assembly deposited on the disk support having a low thermal expansion coefficient. The two-; layer assembly in a first embodiment comprises a first layer made from a metallic material having a high expansion coefficient and a second layer formed from an alloy at ambient temperature :in ~ a martensitic phase and having a transformation towards another crystallographic phase at a tem-perature below the melting temperature of the first layer. In addition, said second layer has a low expansion coefficient and preferably low or moderate adhesion properties with respect to the metal. of the first layer.
Accordlng to a second embodiment, the first layer ~ 5~
which can be degraded at low temperature, i e.
approximate]y 200 C above arnblent ternperature.
More specifically, the present inventlon relates to a reversible memory struc-ture with S thermo-optlcal writir1g or inscription and optical reading, supported by a substrate perfor~ning a forward movement, whereln the substrate is a material having a low expansion coefficient and the inscribable layer deposited on the substrate is formed by at least two individual layers, constituted by a first layer made from a material which, under the action of heat, deforms a second superimposecl layer of a relatively inexpansible alloy which is at ambient temperature in a martensitic phase and lS has a transforrnation to another crystallographic phase at a temperature below the melting te[nperature of the first layer.
BRIEF DESCRIPTlON OF THE DRAWINGS
The invention is descr1bed irl greater detail hereinafter relative to a non-limitative e,nbodiment of the ~emory structure and w-Lth reference to the attached drawings, where-Ln show:
Fig l a diagram showing the state of a martensite in the absence of tension.
2S Fig 2 an equivalent diagram to that of Fig l, but showing a martensite under tension.
Fig 3 an equivalent diagram ~ that of Fig l when a martensite s cornpressed.
Fig 4 a sectional view of a reversible memory structure according to the invention.
5~
DETAILED DESCRIPTION OF THE PREFERRE~ EMBODIMENTS
In order to simpLify the descriptlon, the embodiment chosen for the explanation of the invention is that in which the first layer is metallic, Certain alloys are ch~racterized hy a transformation in the solid phase at a temperature Tt between a generally centre cubic high temperature phase where the atoms are arranged in random manner at the lattice nodes and a ~eneral]y orthorhombic low temperature phase where one or more atom types are located at particular positions and in particular planes of the lattice. This so-cal:Led martensitic transformation is reversible and is generally obtained by a coordinAted she~r process which step by step affects the complete structure.
; It is therefore a very rapid process, because it involves no individual atom migration over long distances.
When thetemperature drops below Tt the "precipitation" of atoms in the preferred planes of the martensite leads to the formation of small inter-- connected plates wi~h variable orientations. Certain - plates are under tension, whilst others are under compression and the internal stress state defines the relative surfaces of the di~ferent types of plates in order to reduce the internal energy to a ~inimum.
Fig l shows two types oE plates which~ for reasons of simplicity, are assumed to develop with the same speed, Plate l is assumed to be under compression ~ ~ 6~5 and plate 2 under tension.
In Fig 2, when a tensile stress is app:l.ied to the material, there is a preferred growth of the p].ates 2 and consequently the structure is cleformed.
If a tensile stress is used in Fig 3, deformation takes place in the other direction. Ct should be noted that this is an overall microscopic deforrnation, without relative sliding of the crystallo-graphic planes, as occurs with conventional plasticdeformation. The resultant effect is the same if the sample is deformed instead of stressed.
In summarizirlg, a deormation in the marten-sitic phase has the added essential interest of lS taking place by she~r and not by interplanar sliding.
Thus, such a deformation can be completely erased by eliminating the martensitic larnellas, this taking place as soon as the -temperature exceeds Tt.
As opposed to this, deformati.ons of the plastic type involving interplanar sliding cannot be erased.
The memory action of a martensitîc crystallo- -gr.aphic structure is utilized in the inventi.on in which an optical disk support is covered by a first layer of a Metal having a high expansion coefficient and by a second layer of an alloy in a martensitic phase and having a transformation point Tt below the melting point of the first layer. Moreover, the alloy rnus~ have ~ low expansion coefficient and prefer~bly low or moderate adhesi~n to the metal of the ~irst layer.
_5_ 5 ~ ~
Fig 4 shows the reverslbl~ memory str~lct~l~e according to the invention~
Onto a preferably flat, rigid and transparent substrate 1 (without -these characteristics being S essential) are deposited a first metal layer 2 and then a second metal layer 3. According to a preferred embodiment of the invention, the first metal layer
Reversible memor structure with thermo-o~~ic riti~
and o~cal readin~ and~~rocess for writln~ and eras-in~
~aid structure.
BACKGR0UND OF ~HE INVENTION
The present invention relates to a reversible memory structure, i.e. it can be thermo-optically written and erased, whilst reading is optica:l.
It applies more particu]arly to the inscription or writing layer of a memory storing data on a moving support. One widely used form of this memory is the optical disk. Optical disks are made from a disk of a rigid and generally kransparent material covered with a thin film of a light-absorbing material. The disk rotates at a relatively high speed and passes in front of a reading head, which detects the data which have been recorded in the surface absorbent layer. r~he data are generally stored in the form of perforations in the absorbent layer. Thus, reading can take place by passing a laser beam through the data storage holes and through the transparent support oE the op~ical disk. It can also be carried out by reAflecting a laser beam through -the transparen-t _ support of the disk onto the absorbent layer. The data can also be stored in the form of a surface defo-rmation in which case reading takes place by reflection.
The existing technology of optical disks or in more general terms moving memories has two types of structure for the t~riting or inscript:ion layer, namely non-e~asable structures such as those in which are made ~.
~ 3 perforations of the metal layer constituting the absorbent layer, or erasable structure.s Erclsable structures are based on the use of arnorphous, metallic or semiconducting materials or magneto-optic, photochromic or photodichroic materialshaving differences in the optical properties depending on whether or not they are inscribed by a laser beam. The general disadvantage o such erasable structures is a low signal~to-no;se ratio because there is no fundamental modification of the structure of the absorbent layer material.
B~IEF SUMMAR~ OF TEIE INVENTION
rfhe invention relates -to a novel reversible memory s~ructure, i.e. it can be erased and re~
inscribed, which has a better signal-to-noise ratio than the known memories. This structure is constituted by a two-layer assembly deposited on the disk support having a low thermal expansion coefficient. The two-; layer assembly in a first embodiment comprises a first layer made from a metallic material having a high expansion coefficient and a second layer formed from an alloy at ambient temperature :in ~ a martensitic phase and having a transformation towards another crystallographic phase at a tem-perature below the melting temperature of the first layer. In addition, said second layer has a low expansion coefficient and preferably low or moderate adhesion properties with respect to the metal. of the first layer.
Accordlng to a second embodiment, the first layer ~ 5~
which can be degraded at low temperature, i e.
approximate]y 200 C above arnblent ternperature.
More specifically, the present inventlon relates to a reversible memory struc-ture with S thermo-optlcal writir1g or inscription and optical reading, supported by a substrate perfor~ning a forward movement, whereln the substrate is a material having a low expansion coefficient and the inscribable layer deposited on the substrate is formed by at least two individual layers, constituted by a first layer made from a material which, under the action of heat, deforms a second superimposecl layer of a relatively inexpansible alloy which is at ambient temperature in a martensitic phase and lS has a transforrnation to another crystallographic phase at a temperature below the melting te[nperature of the first layer.
BRIEF DESCRIPTlON OF THE DRAWINGS
The invention is descr1bed irl greater detail hereinafter relative to a non-limitative e,nbodiment of the ~emory structure and w-Lth reference to the attached drawings, where-Ln show:
Fig l a diagram showing the state of a martensite in the absence of tension.
2S Fig 2 an equivalent diagram to that of Fig l, but showing a martensite under tension.
Fig 3 an equivalent diagram ~ that of Fig l when a martensite s cornpressed.
Fig 4 a sectional view of a reversible memory structure according to the invention.
5~
DETAILED DESCRIPTION OF THE PREFERRE~ EMBODIMENTS
In order to simpLify the descriptlon, the embodiment chosen for the explanation of the invention is that in which the first layer is metallic, Certain alloys are ch~racterized hy a transformation in the solid phase at a temperature Tt between a generally centre cubic high temperature phase where the atoms are arranged in random manner at the lattice nodes and a ~eneral]y orthorhombic low temperature phase where one or more atom types are located at particular positions and in particular planes of the lattice. This so-cal:Led martensitic transformation is reversible and is generally obtained by a coordinAted she~r process which step by step affects the complete structure.
; It is therefore a very rapid process, because it involves no individual atom migration over long distances.
When thetemperature drops below Tt the "precipitation" of atoms in the preferred planes of the martensite leads to the formation of small inter-- connected plates wi~h variable orientations. Certain - plates are under tension, whilst others are under compression and the internal stress state defines the relative surfaces of the di~ferent types of plates in order to reduce the internal energy to a ~inimum.
Fig l shows two types oE plates which~ for reasons of simplicity, are assumed to develop with the same speed, Plate l is assumed to be under compression ~ ~ 6~5 and plate 2 under tension.
In Fig 2, when a tensile stress is app:l.ied to the material, there is a preferred growth of the p].ates 2 and consequently the structure is cleformed.
If a tensile stress is used in Fig 3, deformation takes place in the other direction. Ct should be noted that this is an overall microscopic deforrnation, without relative sliding of the crystallo-graphic planes, as occurs with conventional plasticdeformation. The resultant effect is the same if the sample is deformed instead of stressed.
In summarizirlg, a deormation in the marten-sitic phase has the added essential interest of lS taking place by she~r and not by interplanar sliding.
Thus, such a deformation can be completely erased by eliminating the martensitic larnellas, this taking place as soon as the -temperature exceeds Tt.
As opposed to this, deformati.ons of the plastic type involving interplanar sliding cannot be erased.
The memory action of a martensitîc crystallo- -gr.aphic structure is utilized in the inventi.on in which an optical disk support is covered by a first layer of a Metal having a high expansion coefficient and by a second layer of an alloy in a martensitic phase and having a transformation point Tt below the melting point of the first layer. Moreover, the alloy rnus~ have ~ low expansion coefficient and prefer~bly low or moderate adhesi~n to the metal of the ~irst layer.
_5_ 5 ~ ~
Fig 4 shows the reverslbl~ memory str~lct~l~e according to the invention~
Onto a preferably flat, rigid and transparent substrate 1 (without -these characteristics being S essential) are deposited a first metal layer 2 and then a second metal layer 3. According to a preferred embodiment of the invention, the first metal layer
2 is the layer of the metal having the high expansion coefficient, whilst the second me-tal layer 3 is the alloy layer in a martensitic phase at ambient temperature. Un~er the action of a heat pulse during the inscription of data on the disk, the energy quantity supplied by the laser beam at its impact point with the surface of th;e disk is absorbed by the assembly of the two metal plates and transformed into heat~ The resulting heating at a~temperature T
below ternperature Tt leads to the differential expansion between the two metal layers~; The highly expansible layer 2 imposes on the less expansible 20 layer 3 a ~eformation which is below the brea~ing -~; limit deformation of layer 3. Thus, a relief in _ the form of protuberance 4 is obtained ~or layer 3~
During the deformation of the two layers, at 5 there ; is a disengagement of the two~layer assembly with respect to the substrate. The permanent deformation o laye~ 3 only applies to the martensite plates, without affecting the atomic skeleton Following the impact of the laser beam and during cooling, the expansible layer 2 is disengaged from the marten~
site layer 3, but does not affect data inscription on .
~, the disk.
The present structllre is erasabLe and reversible in the sense that if the martensit:ic layer 3 is raised to a temperature exceeding the transformation point Tt of the rnartensitic phase into its parent phase either by a higher power pu~se, or by a slower displacemen-t of the support in front of the energy source, or by an overall heating7 the alloy is brought into its parent phase and assumes its initial form again by re-adhering to the relatively inextensible layer 2, which has previously assumed its initial form. Following the erasure operation, which takes place at a relatively high temperature, i.e. above the transforrnation point Tt~ the alloy layer 3 returns to the martensitic phase during cooling.
Consequently, starting with a planar structure having a first high]y expansible layer and a second rela-tively inexpansible layer, but in the martensitic phase at arnbient tempera-tur2, it is possible to record data in the forrn of a surface deforrnation o~ the inscribable layer and then erase said data and return to the initial state by a second operation of heating to a temperature above that of a first data inscription operation.
The construction of the memory structure in accordance with the invention involves the use for the layer of highly expansible metal o~ one of khe ollowing materials, considered either individually or in cornbination: cadrnium, zinc, thalium, magn~um, ~ J
aluminium, manganese or silver. The second meta.l layer, i.e. the martens:i.t:i.c phase al:loy layer i.s obtained during a vacuum metalli~ation operation follo~ing the metallization of the first metal layer in the sa[ne frame and wlthout any techn~logy change by the deposition of one of the following alloys in their martensitic phase: iron-nickel, iron-platinum3 titanium-nickel, nickel-aluminium7 gold-cadmium, copper-zinc or stainless s~eels or ternary mixtures such as copper-zinc-aluminium containing 68 to 30% COppeL; L0 to 28% zinc, 4 to 10~/~ alunlinium and in accordance with the formula Cu75Znl8A17, whose transformation point is equal to 170C and the formula Cu79znl3Al8~ whose transfOrmation po~t is equal to 300 C.
The thickness required for each o.E the two layers 2 and 3 in Fig 4 is a~proxirnately 3 to 5 nanometres.
Thi.s type of reversible memory structure has a certain number of practical interests Firstly5 the erasure speed is very high, because there is no atomlc migration. Instead, sheer ~ takes place which affects the entire structure step by step. Thus, in order to erase the inscribed da-ta it is merely necessary to move the recorded memory beneath a laser head supplying a certain energy quantiky, Secondly, this erasable structure ~as a better signa.L to-noise ratio -than other known erasab:Le structllres .
I~ addition, the construction technology i.s ~ , "
simplified, because the deposition of the metal layers 2 and 3 is carried out by one operatln~
: sequence in the same vacuum frame.
Ihe recorded data can be protected due to the state of hardness of the recorded surface by deposit.ing a photosensitive, thermal lacquer, by dissolved polymer varnish or by a preferably transparent, rigid cover which protects the complete surface of the recorded memory.
10 On the basis of these considerations regarding the value of the recorded surface state . it follows that duplication is possible, eOg~ by means of photopolymerizable :Lacquers. Thus, file or archive formation is possible by depositin~ thick metal layers for the purpose o~ storing the recorded ~: data for long periods.
This:erasable memory structure is mainly used in the case of optical disks, but in more general terms can be used for thermo-optical recording : 20 archive formation means and optical reading on rigid or flexible, planar or cyli.ndrical supports effecting . either a rotary or a linear movement.
The scope o~ the invention also covers cases in which there are more than two metal layers, iOe. when the support is firstly covered with a metal attachment layer for the highly expansible metal layer 2, followed ~y a fourth metal layer deposited on the martensitic layer 3. The fourth metal layer provides the surface of the recorded memory with a better reflection state or a protection, ~9- .
-- ~ 3lÇi~5~
eOg. against oxidation.
O~her variants of the inven~ion can be gathered Erom the claims.
'.
-10- , ...
.
~ . .
below ternperature Tt leads to the differential expansion between the two metal layers~; The highly expansible layer 2 imposes on the less expansible 20 layer 3 a ~eformation which is below the brea~ing -~; limit deformation of layer 3. Thus, a relief in _ the form of protuberance 4 is obtained ~or layer 3~
During the deformation of the two layers, at 5 there ; is a disengagement of the two~layer assembly with respect to the substrate. The permanent deformation o laye~ 3 only applies to the martensite plates, without affecting the atomic skeleton Following the impact of the laser beam and during cooling, the expansible layer 2 is disengaged from the marten~
site layer 3, but does not affect data inscription on .
~, the disk.
The present structllre is erasabLe and reversible in the sense that if the martensit:ic layer 3 is raised to a temperature exceeding the transformation point Tt of the rnartensitic phase into its parent phase either by a higher power pu~se, or by a slower displacemen-t of the support in front of the energy source, or by an overall heating7 the alloy is brought into its parent phase and assumes its initial form again by re-adhering to the relatively inextensible layer 2, which has previously assumed its initial form. Following the erasure operation, which takes place at a relatively high temperature, i.e. above the transforrnation point Tt~ the alloy layer 3 returns to the martensitic phase during cooling.
Consequently, starting with a planar structure having a first high]y expansible layer and a second rela-tively inexpansible layer, but in the martensitic phase at arnbient tempera-tur2, it is possible to record data in the forrn of a surface deforrnation o~ the inscribable layer and then erase said data and return to the initial state by a second operation of heating to a temperature above that of a first data inscription operation.
The construction of the memory structure in accordance with the invention involves the use for the layer of highly expansible metal o~ one of khe ollowing materials, considered either individually or in cornbination: cadrnium, zinc, thalium, magn~um, ~ J
aluminium, manganese or silver. The second meta.l layer, i.e. the martens:i.t:i.c phase al:loy layer i.s obtained during a vacuum metalli~ation operation follo~ing the metallization of the first metal layer in the sa[ne frame and wlthout any techn~logy change by the deposition of one of the following alloys in their martensitic phase: iron-nickel, iron-platinum3 titanium-nickel, nickel-aluminium7 gold-cadmium, copper-zinc or stainless s~eels or ternary mixtures such as copper-zinc-aluminium containing 68 to 30% COppeL; L0 to 28% zinc, 4 to 10~/~ alunlinium and in accordance with the formula Cu75Znl8A17, whose transformation point is equal to 170C and the formula Cu79znl3Al8~ whose transfOrmation po~t is equal to 300 C.
The thickness required for each o.E the two layers 2 and 3 in Fig 4 is a~proxirnately 3 to 5 nanometres.
Thi.s type of reversible memory structure has a certain number of practical interests Firstly5 the erasure speed is very high, because there is no atomlc migration. Instead, sheer ~ takes place which affects the entire structure step by step. Thus, in order to erase the inscribed da-ta it is merely necessary to move the recorded memory beneath a laser head supplying a certain energy quantiky, Secondly, this erasable structure ~as a better signa.L to-noise ratio -than other known erasab:Le structllres .
I~ addition, the construction technology i.s ~ , "
simplified, because the deposition of the metal layers 2 and 3 is carried out by one operatln~
: sequence in the same vacuum frame.
Ihe recorded data can be protected due to the state of hardness of the recorded surface by deposit.ing a photosensitive, thermal lacquer, by dissolved polymer varnish or by a preferably transparent, rigid cover which protects the complete surface of the recorded memory.
10 On the basis of these considerations regarding the value of the recorded surface state . it follows that duplication is possible, eOg~ by means of photopolymerizable :Lacquers. Thus, file or archive formation is possible by depositin~ thick metal layers for the purpose o~ storing the recorded ~: data for long periods.
This:erasable memory structure is mainly used in the case of optical disks, but in more general terms can be used for thermo-optical recording : 20 archive formation means and optical reading on rigid or flexible, planar or cyli.ndrical supports effecting . either a rotary or a linear movement.
The scope o~ the invention also covers cases in which there are more than two metal layers, iOe. when the support is firstly covered with a metal attachment layer for the highly expansible metal layer 2, followed ~y a fourth metal layer deposited on the martensitic layer 3. The fourth metal layer provides the surface of the recorded memory with a better reflection state or a protection, ~9- .
-- ~ 3lÇi~5~
eOg. against oxidation.
O~her variants of the inven~ion can be gathered Erom the claims.
'.
-10- , ...
.
~ . .
Claims (7)
1. A reversible memory structure with thermo-optical writing or inscription and optical reading, supported by a substrate performing a forward movement, wherein the substrate is a material having a low expansion coefficient and the inscribable layer deposited on the substrate is formed by at least two individual layers, constituted by a first layer made from a material which, under the action of least deforms a second superimposed layer of a relatively inexpansible alloy which is at ambient temperature in a martensitic phase and has a transformation to another crystallographic phase at a temperature below the melting temperature of the first layer
2. A memory structure according to claim 1, wherein the first layer is a highly expansible metal layer and made from the following metals: Cd, Zn, Ti, Mg, Al, Mn, Ag, considered individually or in alloy form.
3. A memory structure according to claim 1, wherein the first layer is a polymer layer which can be degraded by heating.
4. A memory structure according to claim 1, wherein the martensitic layer is produced from one of the following alloys: stainless steel, Fe-Ni, Fe-Pt, Ti-Ni, N-Al, Au-Cd, Cu-Zn, Cu-Zn-Al.
5. A memory structure according to claim 1, wherein inscription leads to a deformation of the martensitic layer, said deformation being less than the breaking limit of said martensitic layer.
6. An inscription or writing process in a memory structure according to claim 1, wherein the inscription means is an energy pulse supplied by a laser beam and absorbed by the double metal layer of the structure in which it is transformed into heat, the energy quantity supplied being sufficient for the first expansible metal layer to deform the second martensitic alloy layer, the temperature remaining below the transformation point of the martensitic phase into another phase.
7.An erasure process of a memory structure in which data has been inscribed according to claim 6, wherein the erasure means comprise an energy pulse supplied by a laser beam and absorbed by the double metal layer of the structure in which it is trans-formed into heat, the energy quantity supplied being adequate to erase the second alloy layer to a temperature above the transformation point of the martensitic phase into another phase.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8002245A FR2475270A1 (en) | 1980-02-01 | 1980-02-01 | REVERSIBLE MEMORY STRUCTURE, THERMO-OPTICAL INTEGRATION AND OPTICAL READING, AND METHOD FOR INSCRIPTION AND ERASURE OF THIS STRUCTURE |
| FR8002245 | 1980-02-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1164560A true CA1164560A (en) | 1984-03-27 |
Family
ID=9238113
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000369792A Expired CA1164560A (en) | 1980-02-01 | 1981-01-30 | Reversible thermo-optical memory structure |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4371954A (en) |
| EP (1) | EP0033667B1 (en) |
| JP (1) | JPS56124136A (en) |
| CA (1) | CA1164560A (en) |
| DE (1) | DE3161717D1 (en) |
| FR (1) | FR2475270A1 (en) |
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| DE3377173D1 (en) * | 1982-09-29 | 1988-07-28 | Toshiba Kk | Radiation-sensitive carrier body utilized as stamper structure |
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| US4852075A (en) * | 1983-08-22 | 1989-07-25 | Optical Data, Inc. | Erasable optical data storage medium and method and apparatus for recording data on the medium |
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| US4638335A (en) * | 1983-12-29 | 1987-01-20 | Xerox Corporation | Optical recording member |
| JPH066393B2 (en) * | 1984-03-07 | 1994-01-26 | 株式会社日立製作所 | How to record and delete information |
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| JPS6144690A (en) * | 1984-08-10 | 1986-03-04 | Res Dev Corp Of Japan | Photo-recording material |
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| JP2987223B2 (en) * | 1991-02-20 | 1999-12-06 | ティーディーケイ株式会社 | Optical recording medium |
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| KR100224804B1 (en) * | 1992-09-15 | 1999-10-15 | 윤종용 | Video multiplexing system |
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| US5363200A (en) * | 1992-09-15 | 1994-11-08 | Samsung Electronics Co., Ltd. | Buffering method and system for resonant scanner used to read and write data with respect to a storage medium |
| US5392272A (en) * | 1993-03-29 | 1995-02-21 | Sri International | Single erasable optical recording layer having both retention and expansion characteristics |
| FR2786790B1 (en) * | 1998-12-04 | 2001-02-23 | Ecole Polytech | LASER PROCESSING OF AN OBJECT OF SHAPE MEMORY MATERIAL |
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|---|---|---|---|---|
| CA967365A (en) * | 1970-10-12 | 1975-05-13 | Fuji Photo Film Co. | Laser recording method and material therefor |
| US3866187A (en) * | 1973-07-02 | 1975-02-11 | Philips Corp | Method of recording and reproducing information in ferroelastic metals |
| FR2368779A1 (en) * | 1976-10-22 | 1978-05-19 | Thomson Brandt | THERMOSENSITIVE MEDIA INTENDED FOR RECORDING INFORMATION AND PROCESS FOR RECORDING INFORMATION ON SUCH MEDIA |
| CH604215A5 (en) * | 1976-12-21 | 1978-08-31 | Landis & Gyr Ag | |
| DE2744533A1 (en) * | 1977-10-04 | 1979-04-12 | Polygram Gmbh | Laser recording media, esp. disks - where recording layer is cover by transparent protective lacquer |
| JPS553971A (en) * | 1978-06-26 | 1980-01-12 | Fuji Photo Film Co Ltd | Thermal recording material |
-
1980
- 1980-02-01 FR FR8002245A patent/FR2475270A1/en active Granted
-
1981
- 1981-01-06 DE DE8181400004T patent/DE3161717D1/en not_active Expired
- 1981-01-06 EP EP81400004A patent/EP0033667B1/en not_active Expired
- 1981-01-27 US US06/228,990 patent/US4371954A/en not_active Expired - Lifetime
- 1981-01-29 JP JP1090781A patent/JPS56124136A/en active Granted
- 1981-01-30 CA CA000369792A patent/CA1164560A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE3161717D1 (en) | 1984-02-02 |
| EP0033667B1 (en) | 1983-12-28 |
| JPH0262900B2 (en) | 1990-12-26 |
| JPS56124136A (en) | 1981-09-29 |
| FR2475270B1 (en) | 1985-02-08 |
| FR2475270A1 (en) | 1981-08-07 |
| EP0033667A1 (en) | 1981-08-12 |
| US4371954A (en) | 1983-02-01 |
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